Aluminum suspension pivots

[boyracer]

Hi everybody. Just curious as to what grade of aluminium is used to make the rocker arms in pushrod suspension.
Lots of racecars use pushrod suspension and I have a project forming in the back of my mind that I would like to use it for.
I know they are very stressed, and have to take some fairly large loads, so I presume they're some sort of aircraft grade aluminium, but does anyone know the specifics.
Also due to the fatigue limit of aluminium being much lower than steel do they need to be replaced reguarly ? Project in mind would be a club car, would appreciate any thoughts on the matter.
Also have read about building racecars from carbon fibre or aluminium honeycomb but want to know more of the practical side, can anyone suggest books or website ?

[Sean]

what is your project that you need to design the rocker arms for? I also want to look into carbon fibre frames... Let me know if you find anything that is usefull (i.e. detailed info)

[Griff]

The grade of alluminium you are looking for is HE 30
Very good strength but easy to machine.
Only thing is I'm not shure if your system of grading is the same as ours
hope this helps
GRIFF

[boyracer]

Thanks for the reply Griff, I'll call my local material supplier and see if they can translate it for me.

[steve bang]

Hey guys check the Britten motorcycle as the suspension parts in them is carbon fibre so may give you an idea of stresses involved. www.britten.co.nz

[ISK]

The grade of aluminium used will depend greatly on the forces (and hence stresses) applied. If the stresses are kept to a reasonable level, fatigue will probably not be a significant factor as the number of load reversals will be low (less than a million) for the life of the item. The important thing when designing to combat fatigue is to avoid any sharp internal corners or rapid changes in cross-section. Imagine the loads in you item are like race cars on a circuit. Faced with a tight 90 deg bend on lap one, the cars (stresses) will bunch up. If the corner is long and sweeping there will be much less bunching and therefore lower local stresses.
If you haven't had any luck finding some material try some of the American aerospace designations i.e. 6061. 2014 or 2024. The strength increases as I've listed them. Most of the Ali in the world comes from the states so US designations are generally easier to get. Failing that you could try and get some good old fashion British aerospace grade stuff like BS.L91 (Plate stock upto 2" thick) or BS.L168 (Bar stock upto 10" ruling section).
If you need some detailled data on the materials I've quoted send a reply and I'll see what I can do.